#define _CRT_SECURE_NO_WARNINGS
class Solution {
public:
    vector<vector<int>> fourSum(vector<int>& nums, int target) {
        vector<vector<int>> ret;
        sort(nums.begin(), nums.end());
        int n = nums.size();
        int i, j;
        for (i = 0; i < n; )
        {
            for (j = i + 1; j < n; )
            {
                int left = j + 1, right = n - 1;
                while (left < right)
                {
                    long sum = nums[left] + nums[right];
                    if (sum > (long)target - nums[i] - nums[j]) right--;
                    else if (sum < (long)target - nums[i] - nums[j]) left++;
                    else
                    {
                        ret.push_back({ nums[i], nums[j], nums[left], nums[right] });
                        left++, right--;
                        while (left < right && nums[left] == nums[left - 1]) left++;
                        while (left < right && nums[right] == nums[right + 1]) right--;
                    }
                }
                j++;
                while (j < n && nums[j] == nums[j - 1]) j++;
            }
            i++;
            while (i < n && nums[i] == nums[i - 1]) i++;
        }
        return  ret;
    }
};